The gapfill process is a very important stage of semiconductor manufacturing. The gapfill process is used to fill a high aspect ratio gap (or feature) with an insulating or conducting material. For example, shallow trench isolation, inter-metal dielectric layers, passivation layers, dummy gate, etc. As device geometries shrink (e.g., critical dimensions <20 nm) and thermal budgets are reduced, defect-free filling of spaces becomes increasingly difficult due to limitations of conventional deposition processes.
Most deposition methods deposit more material on the top region than on the bottom region of a structure. The process often forms a mushroom shape film profile. As a result, the top part of a feature sometimes pinches off prematurely leaving seams or voids within the structure's lower portions. This problem is more prevalent in small features.
Atomic layer deposition of tungsten for gap filling has been demonstrated to be a key technology in semiconductor industry. However, the seam in the gap fill is a limitation in ALD tungsten deposition. Therefore, there is need for a method to create a seamless tungsten fill.